The water felting of dilute aqueous dispersions of mineral wool and/or lightweight aggregate is a well-known commercial process for manufacturing acoustical ceiling tile. In this process, an aqueous slurry of mineral wool, lightweight aggregate, cellulosic fiber, starch binder and other ingredients, as desired or necessary, is flowed onto a moving foraminous support wire, such as that of a Fourdrinier or Oliver mat forming machine, for dewatering. The slurry may be first dewatered by gravity and then dewatered by vacuum suction means to form a basemat. The wet basemat is then pressed (with or without the application of additional vacuum) to the desired thickness between rolls and the support wire to remove additional water. The pressed basemat is then dried in heated drying ovens, and the dried material is cut to the desired dimensions and optionally sanded and/or top coated, such as with paint, to produce acoustical ceiling tiles and panels.
Mineral wool acoustical tiles are very porous which is necessary to provide good sound absorption. The prior art (e.g. U.S. Pat. Nos. 3,498,404; 5,013,405; 5,047,120 and 5,558,710) also discloses that mineral fillers may be incorporated into the composition to improve sound absorbing properties and to provide lightweight acoustical tiles and panels.
Acoustical tile compositions must contain a binder and usually employ starch as the binder. The prior art (e.g. U.S. Pat. Nos. 5,911,818 and 5,964,934) suggest that as much as 15% by weight of the composition may be starch although about 6 or 7% by weight is conventionally used.
The prior art (e.g. U.S. Pat. No. 5,250,153) also describes the use of latex binders for acoustical tile compositions and a wide variety of vinyl latex binders have been suggested for this purpose.
It is an object of this invention to provide an acoustical tile composition wherein a wet-strength resin such as a polyamine epichlorohydrin resin replaces the conventional starch binder and the resulting composition may be more efficiently fabricated into acoustical tiles and panels in a water felting process.
It is a further object of this invention to provide an acoustical tile composition wherein the conventional starch binder is replaced by a polyamine epichlorohydrin resin to provide compositions that may be more efficiently fabricated into acoustical tiles and panels having improved performance in high humidity conditions. These and other objects will be apparent to persons skilled in the art in view of the description that follows.